It is well established that the ferric uptake regulatory protein (Fur) functions as a repressor of gene transcription in a number of diverse microorganisms. In the previously funded RO1 we conducted studies to test the hypothesis that in Neisseria gonorrhoeae and N. meningitidis the Fur protein functions as a global regulatory protein as both a repressor and activator of gene transcription. We established in N. gonorrhoeae by in silico analysis, DNA binding studies, and transcriptional analysis, that the partial gonococcal Fur regulon included genes that were both repressed or activated by iron. We also demonstrated that several genes encompassing the N. gonorrhoeae Fur regulon are expressed during natural gonococcal infection. Using DNA microarray technology we demonstrated that in N. meningitidis, more than 200 genes are regulated in response to growth with iron (repressed or activated) and that approximately 50% of these genes had the potential to be regulated by Fur. Recent analysis of a newly constructed N. gonorrhoeae fur mutant have identified several genes whose transcription is regulated by Fur, but too which the Fur protein does not bind to operator regions suggesting that Fur could function indirectly to activate transcription of these genes. Based on these observations we propose that N. gonorrhoeae Fur functions as an activator of transcription through both direct and indirect mechanisms. Whereas the repressive mechanisms of Fur have been thoroughly investigated, the mechanisms of direct and indirect -activation by this protein have not been elucidated. This study is positioned to define the mechanisms by which Fur functions to activate gene transcription and the following Aims are proposed: Aim 1. To fully define and characterize the complete N. gonorrhoeae Fur regulon. Aim 2. To characterize Fur mediated transcriptional activation through an indirect mechanism in which Fur functions to repress a repressor. Aim 3. To characterize Fur mediated transcriptional activation through an indirect mechanism in which Fur functions through small regulatory RNAs. Aim 4. To characterize Fur mediated transcriptional activation through a direct mechanism in which Fur interacts with the operator regions of Fur activated genes. Molecular characterization of the mechanisms by which Fur functions as an activator will yield new information on the control of gene transcription in this sexually transmitted pathogen.